1. Field of the Invention
The present invention relates to a composite sintered body and a LC composite electronic component, and more particularly to a composite sintered body of dielectric substance and magnetic substance having both dielectric properties and magnetic properties which is used in an EMI (Electro Magnetic Interference) filter for high frequency noise reduction of electronic apparatuses, and a LC composite electronic component.
2. Description of the Related Art
Until now, an EMI filter has been widely used for high frequency noise reduction of electronic apparatuses. However, in recent years, properties of an EMI filter capable of being used at a high frequency band in a range from several hundred MHz to several GHz are in demand, to comply with high frequency mobile communication apparatuses such as mobile phones, wireless LANs and the like.
Generally, it has been required that the EMI filter which is used for noise reduction of electronic apparatuses is miniaturized, to comply with the miniaturization of electronic apparatuses.
For this reason, a noise filter has been proposed, in which a coil is formed by silver electrode and the like, in the inside of a composite ceramic where the mixture of magnetic substance and dielectric substance has been fired.
As a magnetic material used for such a composite ceramic, a spinel type ferrite such as Mn—Zn based, Ni—Zn based, Ni—Cu—Zn based and the like, which has a high magnetic permeability in a frequency region between several MHz and several hundred MHz, has been widely used.
In recent years, a hexagonal ferrite material of which the magnetic permeability extends to a frequency region higher than the frequency limit of the spinel type ferrite, has been proposed as a magnetic material in a frequency region between several hundred MHz and several GHz.
The hexagonal ferrite is easily magnetized in a direction of a axis, which hereinafter is called an easy magnetization axis, in a plane perpendicular to the c axis which is so called easy magnetizasion axis, and it is a magnetic material called as a ferrox-planar type ferrite. As a typical ferrox-planar type ferrite of a magnetic material, 3BaO.2CoO.I2Fe2O3 which is Co substituted Z type hexagonal ferrite, 2BaO.2CoO.6Fe2O3 which is Co substituted Y type hexagonal ferrite, BaO.2CoO.8Fe2O3 which is Co substituted W type hexagonal ferrite and the like, are known.
Meanwhile, as a dielectric material used for the composite ceramic, paraelectrics such as CaTiO3, SrTiO3, glass and the like, and ferroelectrics such as BaTiO3 and the like, can be exemplified.
If a composite ceramic material having a high magnetic permeability and a high dielectric constant is realized, the miniaturization of electronic apparatuses can be attained. Therefore, a composite ceramic material having both properties is required.